The data link layer is layer two in the Open Systems Interconnection (OSI) model, this layer is used for nodes communicating over a single network such as a LAN, layer two packets cannot be transmitted from one network to another. The address system that the data link layer uses is the MAC address, these are 48-bit addresses that are assigned to each network interface, on each network the MAC address must be unique.
Technipages Explains Data Link Layer
The OSI model describes seven standard layers of computer networking that handle the addressing and structure of every stage between the application layer where programs state what data they want to transmit, to the physical layer where all data is represented in pure binary for transmission and back.
In the OSI model, the physical layer is the lowest layer and deals with the raw binary of the data in transmission. The data link layer is the second layer dealing with transmissions inside a single network. The network layer is for communication between networks and uses IP addresses to uniquely identify hosts.
The data link layer’s address structure is completely flat, in that the addresses do not imply any sort of logical or physical structure. MAC addresses have an organised structure where the first half of the address is a manufacturer identifier as allocated by the IEEE, the second half of the MAC address is random and is generally assigned when a Network Interface Controller (NIC) is made. It is possible to manually modify or spoof the MAC address of a NIC, although this requires special software to perform.
Common Uses of Data Link Layer
- Besides framing, the data link layer also includes mechanisms to detect and even recover from transmission errors.
- Data-link frames do not cross the boundaries of a local area network.
- The data link layer is the sixth of seven networking layers in the OSI model.
Common Misuses of Data Link Layer
- The data link layer uses IP addresses as its address structure.